A variety of types of ball-point pen refills have been provided.
For example, there is provided a so-called pressurized ball-point pen refill comprising an ink storage tube, a tip fixed to the ink storage tube at an end and a tail plug provided at an end of the storage tube opposite to the tip, wherein ink is filled in the space of the ink storage tube relatively near to the tip, and pressuring gas is filled in the space of the ink storage tube relatively far from the tip, the ink being squeezed to flow toward the tip under the pressure of the pressuring gas.
This pressurized ball-point pen refill enables writing even with the tip turned upward because the pressuring gas constantly squeezes the ink to flow toward the tip.
In the pressurized ball-point pen refill described above, however, there have been cases where the ink leaks from the leading end of the tip under the pressure of the pressuring gas. In addition, there have been cases where a ball drops out from a ball house under the pressure of the pressuring gas.
For preventing such problems, in the pressurized ball-point pen refill, the ball house is formed to have a small inner diameter relative to the diameter of the ball.
However, if the ball house is formed to have a small inner diameter relative to the diameter of the ball, the width of an ink passage in the vicinity of the leading end of the tip is reduced, and therefore problems such as faint lines and degradation in initial writing performance may arise.
In addition, for preventing the problems such as the faint lines and the degradation in initial writing performance while the ball house is formed to have a small inner diameter relative to the diameter of the ball, the ball is formed to have a relatively rough surface.
However, if the ball has an extremely rough surface, a ball seat becomes more prone to wear, and therefore durability of the tip may decline, resulting in a reduction in a writable distance.
That is, in the pressurized ball-point pen refill, it is very difficult to prevent ink leakage and ball dropout, to prevent also the faint lines and the degradation in the initial writing performance, and to increase the writable distance.
Moreover, in the pressurized ball-point pen refill described above, there have been cases where the pressure of the pressuring gas causes the ink to leak from the leading end of the tip.
For preventing the ink leakage, the ink is adjusted to have a relatively high viscosity in the pressurized ball-point pen refill.
However, if the ink is adjusted to have an extremely high viscosity, problems such that writability becomes heavy, that the faint lines tends to occur, and that the initial writing performance is degraded may arise.
On the other hand, if the ink is adjusted to have a low viscosity, the problems can be eliminated, but the ink may leak from the leading end of the tip.
For preventing the ink from leaking from the leading end of the tip, the pressuring gas is adjusted to have a relatively low pressure.
However, if the pressuring gas is adjusted to have an extremely low pressure, problems such that the faint lines tend to occur, and that the initial writing performance is degraded may arise. In addition, if the pressuring gas is adjusted to have an extremely low pressure, the pressure of the pressuring gas may decrease to an atmospheric pressure before the ink is fully used, resulting in that the pen cannot write while the ink remains in the ink storage tube. In other words, the writable distance may decrease.
On the other hand, if the pressuring gas is adjusted to have a high pressure, the problems can be eliminated, but the ink may leak from the leading end of the tip.
That is, in the pressurized ball-point pen refill, it is very difficult to prevent the ink leakage, to prevent also the faint lines and the degradation in the initial writing performance, and to sufficiently increase the writable distance.
Moreover, if the ink storage tube is formed to have a relatively small inner diameter, a capillary force can easily act within the ink storage tube, and the ink filled in the ink storage tube becomes hard to flow toward the end opposite to the tip even with the tip turned upward.
In the pressurized ball-point pen refill described above, however, both the ink and the pressuring gas should be filled in the ink storage tube, and, therefore, if the ink storage tube is formed to have a relatively small inner diameter, a filling space of the pressuring gas should be made relatively small, a filling amount of the ink should be made relatively small, or the ink storage tube should be formed to have a relatively large length.
However, if the filling space of the pressuring gas is made relatively small, the pressure of the pressuring gas may decrease to an atmospheric pressure before the ink is fully used, whereby the ink cannot be used to the end. Moreover, for making the filling space of the pressuring gas relatively small, and for also ensuring that the ink can be fully used, the pressuring gas should be adjusted to have a relatively high pressure, but, if so, the ink may leak from the leading end of the tip.
Moreover, if the amount of filled ink is made relatively small, the writable distance becomes relatively short.
Moreover, if the ink storage tube is formed to have a relatively large length, the total length of the ball-point pen refill becomes relatively large, but there is some limit on the length of the ball-point pen refill, and, therefore, the ink storage tube cannot be formed to have an unreasonably large length.
Thus, in the pressurized ball-point pen refill described above, the ink storage tube is formed to have a relatively large inner diameter.
However, if the ink storage tube is formed to have a large inner diameter, a capillary force becomes hard to act within the ink storage tube, and, therefore, the ink filled in the ink storage tube tends to flow toward the end opposite to the tip.
Thus, in the pressurized ball-point pen refill, the ink storage tube is formed to have a relatively large inner diameter, and a float traveling according to the decrease of the ink amount is provided between the ink and the pressuring gas to prevent the ink from flowing toward the end opposite to the tip.
However, even if the float is provided between the ink and the pressuring gas, the ink may flow toward the end opposite to the tip through a gap between the ink storage tube and the float if the outer diameter of the float is too small relative to the inner diameter of the ink storage tube.
On the other hand, if the outer diameter of the float is too large relative to the inner diameter of the ink storage tube, it maybe impossible to allow the float to travel smoothly according to the decrease of the ink amount.
That is, in the pressurized ball-point pen refill, it is very difficult to prevent outflow of the ink toward the end opposite to the tip.